Intro to Bones + Soft Tissue Flashcards
What is a joint?
point at which 2 separate bones meet
What is the muscoskeletal system made up of?
- bone
- muscle
- connective tissue
What are the 3 different types of connective tissue?
- tendon
- ligament
- cartilage
How many bones in an adult skeleton?
206
How many bones in a child?
270
What are the 2 main parts of the skeleton?
Appendicular + Axial
What is a part of the axial skeleton?
- cranium
- vertebral column
- ribcage
What is a part of the appendicular skeleton?
- pectoral girdle
- upper + lower limbs
- pelvic girdle
What are the functions of the skeleton?
- Movement
- Support
- Protection of vital organs
- Calcium storage
- Haematopoesis
What are the 2 ways in which bones develops “in utero”?
Intramembranous + endochondral
What is intramembranous ossification?
• bone develops from fibrous membranes to
become mesenchymal cell template
• forms flat bones of skull, clavicle + mandible
What is endochandral ossification?
- development of long bone from a hyaline cartilage model (first model)
- takes much longer than intramembranous ossification
What are the 5 steps of endochondral ossification?
- bone collar formation
- cavitation
- periosteal bud invasion
- diaphysis elongation
- epiphyseal ossification
What are the 4 main cells of bones?
- osteogenic
- osteocyte
- osteoblast
- osteoclast
What are osteogenic cells?
bone stem cell
found in deep layers of periosteum
Where can you find osteogenic cells?
deep layers of periosteum
What are osteoblasts?
What do they do?
- bone forming
- secretes osteoid
- catalyse mineralisation of osteoid
Where can you find osteoblasts?
growing portions of bone, including periosteum + endosteum
What are osteoclasts? What do they do?
- bone breaking
- dissolve + reabsorb bone by phagocytosis
- derived from bone marrow
Where can you find osteoclasts?
growing portions of bone, including periosteum + endosteum
What are osteocytes?What do they do?
• mature bone cell • formed when osteoblast becomes embedded in its secretions • sense mechanical strain to direct osteoclast and osteoblast activity
Where can you find osteocytes?
embedded in matrix
What is bone matrix? How is it organised?
- 40% organic
* 60% organic
What is the organic component of bone matrix made up of?
- 90% type 1 collagen
* 10% ground substance
What is the inorganic component of bone matrix made up of?
- calcium hydroxyapatite
* osteocalcium phosphate
What is the ground substance of bone matrix made up of?
- proteoglycans
- glycoproteins
- cytokine + growth factors
What are the 2 types of bone?
- immature
* mature
What is immature bone?
- first bone produced
- laid down in a ‘woven’ manner – relatively weak
- mineralised + replaced by mature bon
What is mature bone?
- mineralised woven bone
* lamellar (layer) structure – relatively strong
What are the 2 types of mature bone?
- cortical
* cancellous
What is cortical bone?
- compact + dense
* suitable for the stresses of weight bearing
What is cancellous bone?
- spongy structure
* not suitable for weight-bearing
What is an osteon?
- repeated structural units
* concentric lamellae around a central Haversian Canal
How are cortical bones organised?
• Few spaces • ‘Osteons’ • Haversian Canal – contains blood vessels, nerves and lymphaVcs. • Lacunae – small spaces containing osteocytes • Tiny canaliculi radiate from lacunae filled w/ extracellular fluid • Volkmans canal – transverse perforating canals
What is the structure of long bones?
- proximal epiphysis
- metaphysis
- diaphysis
- metaphysis
- distal epiphysis
What are the 2 methods of bone growth?
- interstitial
* appositional
What is interstitial bone growth?
long bone lengthening (increasing length)
What is appositional growth?
deposition of bone
beneath the periosteum to increase thickness (increasing width)
What are the 4 zones / steps in interstitial growth?
- proliferation
- hypertrophic/maturation
- calcification
- ossification
What is the importance of bone in increasing calcium serum levels?
→ Bone contains 99% of total body calcium
→ PTH stimulates calcium release from bone
→ osteoclasts activity > osteoblasts activity
What is the importance of bone in decreasing calcium serum levels?
m
What is the importance of calcium hydroxyapatite?
m
How are joints classified?
Fibrous (synarthrosis)
Cartilaginous (Amphiarthrosis)
Synovial (Diarthrosis)
What are the fibrous joints? Examples?
- Sutures
- Syndesmosis
- Interosseous membrane
What are cartilaginous joints? Examples?
- Synchondroses
* Symphyses
What are synovial joints? Examples?
- Plane, Hinge, Condyloid
* Pivot, Saddle, Ball & Socket
What is the structure of a synovial joint?
Joint capsule:
• Articular capsule (outer) keeps bones together structurally
• Synovial membrane (inner) - contains synovial fluid which reduces friction during movement
What factors affect joint stability?
- Joint shape e.g. hip vs shoulder
- Ligaments
- Tendons
- Cartilage (e.g. glenoid labrum)
What are ligaments made up of?
90% Type 1 collagen (strong)
9% Type 3 collagen (immature; greater in healing tissue)
1% fibroblast cells (produce collagen)
What is the function of a ligament?
Connect bone to bone to stabilise joint and enable proprioception ‘
What is collagen?
- Most abundant protein in the human body
- Molecule is a long, rigid structure
- 3 polypeptides (referred to as α chains) are wound around one another
- Rope-like triple helix
- Crimping of fibres
- Non-elastic behaviour
- Fibre component of connective tissue
What is a tendon?
- Made of collagen fibres arranged in bundles
- Stiff and Strong
- Parallel arrays of collagen fibres closely packed together
What is the microstructure of a tendon?
Parallel arrays of collagen fibres closely packed together
What is the function of a tendon?
- Attaches skeletal muscle to bone
- Transmits muscle force to bone
- Elastic energy storage/recoil
- Proteoglycan resists compressive stresses
What is cartilage?
- Made up of chondrocytes which produce large amounts of collagenous ECM, ground substance
- Avascular and worn down in osteoarthritis
What is the function of cartilage?
- Acts as shock absorber to reduce friction
- Covers and protects long bones at joints
- Structural component of ribs & intervertebral discs
What are the 3 types of cartilage?
Elastic Hyaline
Fibrocartilage
How do ligaments affect joint stability?
- Ligaments prevent excessive movement that could damage joint
- More ligaments and tighter ligaments = greater stability BUT less mobility
- Less ligaments and laxer ligaments = greater mobility BUT less stability
What is the problem of poor stability in a joint?
Risk of dislocation
What is the problem with lax ligaments in joints?
Hypermobility = greater risk of injury
What is the problem w/ repeated or inappropriate stress to ligaments?
Increases risk of injury
What is periosteum?
dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints
What is a medullary cavity?
central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored
What is epiphysis?
end part of a long bone, initially growing separately from the shaft
What is metaphysis?
- neck portion of long bone between epiphysis + diaphysis
* contains the growth plate
What is diaphysis?
shaft or central part of bone
What is step 1 of intramembranous ossification?
condensation of mesenchymal cells which differentiate into osteoblasts to form ossification centre
What is step 2 of intramembranous ossification?
secreted osteoid traps osteoblasts which become osteocytes
What is step 3 of intramembranous ossification?
trabecular matrix and periosteum form
What is step 4 of intramembranous ossification?
compact bone develops superficial to cancellous bone + crowded blood vessels develop into blood vessels
Where is the primary ossification centre?
diaphysis
Where is the secondary ossification centre?
epiphysis
What is the proliferation zone in interstitial growth?
cells proliferate + push epiphyses away from diaphysis
What is the hypertrophic / maturation zone in interstitial growth?
- cartilage cells swell in size (called hypertrophy)
- lacunae get larger
- results in the formation of large spaces
What is the calcification zone in interstitial growth?
- cartilage is calcified at the juncture of diaphysis + epiphyses
- matrix breaks down
- blood vessels enter the spaces
What is the ossification zone in interstitial growth?
- marrow from medullary cavity enters calcified cartilage
* osteoclasts break down cartilage + osteoblasts replace it with new spongy bone
What is the epiphyseal plate?
zone of elongation in long bones, contains hyaline cartilage
What zones or steps of interstitial growth are on the epiphyseal side?
- proliferation
* hypertrophy
What zones or steps of interstitial growth are on the diaphyseal side?
- calcification
* ossification
What is step 1 of appositional growth?
ridges in the periosteum create a groove for
periosteal blood vessel
What is step 2 of appositional growth?
periosteal ridges fuse, forming an endosteum-lined tunnel
What is step 3 of appositional growth?
osteoblasts in endosteum build new concentric
lamellae inward towards the centre of the tunnel, forming a new osteon
What is step 4 of appositional growth?
bone grows outwards as osteoblasts in periosteum build new circumferential
lamellae. Osteon formation repeats as new periosteal ridges fold over blood vessel
